A 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) communication system will be described as an exemplary wireless communication system to which the present invention can be applied.
FIG. 1 is a schematic view illustrating an Evolved Universal Mobile Telecommunications System (E-UMTS) network configuration as an exemplary wireless communication system. E-UMTS is an evolution of the legacy UMTS. E-UMTS is under basic standardization in the 3GPP. In general, it can be said that E-UMTS is an LTE system. For details of the UMTS and E-UMTS technical specifications, refer to Release 7 and Release 8 in “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.
Referring to FIG. 1, the E-UMTS system includes a User Equipment (UE), evolved Node Bs (eNode Bs or eNBs), and an Access Gateway (AG) which is located at an end of the network (E-UTRAN), connected to an external network. An eNode B can simultaneously transmit multiple data streams for broadcast service, multicast service and/or unicast service.
A single eNode B manages one or more cells. A cell is set to operate in one of the bandwidths of 1.44, 3, 5, 10, 15, and 20 Mhz and provides downlink or uplink transmission service to a plurality of UEs. Different cells may be set to provide different bandwidths. The eNode B controls data transmission and reception to and from a plurality of UEs. Regarding DownLink (DL) data, the eNode B signals information about a time/frequency area, coding scheme, data size, Hybrid Automatic Repeat and reQuest (HARQ) information, etc. for data transmission to a UE by DL scheduling information. Regarding UpLink (UL) data, the eNode B signals information about a time/frequency area, coding scheme, data size, Hybrid Automatic Repeat and reQuest (HARQ) information, etc. available to the UE by UL scheduling information. An interface for transmitting user traffic or control traffic may be used between eNode Bs. A Core Network (CN) may be configured with an AG and a network node for performing user registration of a UE. The AG manages the mobility of UEs on a Tracking Area (TA) basis. A TA is composed of a plurality of cells.
Although wireless communication technology has reached the developmental stage of LTE based on Wideband Code Division Multiple Access (WCDMA), demands and expectations of users and service providers are ever increasing. Considering that other radio access technologies are being developed, new technological evolutions are required to achieve future competitiveness. There exists a need for reduction of cost per bit, increase of service availability, flexible use of frequency bands, simplified structures and open interfaces, and appropriate power consumption of UEs.